328 Memoirs of the Caledonian Horticultural Society. 



" These last experiments prove that vegetation is affected by the metal- 

 lic poisons, sulphate of copper, acetate of lead, and corrosive sublimate, 

 and perish under their influence. They also prove that ferruginous matter 

 holds the first rank in these deadly poisons ; and, in this respect, there is 

 a difference between animal and vegetable life. When iron obtains in any 

 soil, there is an enemy to contend with; and sand and lime, in due pro- 

 portions, appear to me to be the only remedy : the lime decomposing the 

 salt of iron, and the silica combining, in the character of an acid, with the 

 oxide thus separated. Such a combination we find in the baths of Lucca, 

 &c. The experiments also show the comparative fatality, and yield decided 

 evidence of the passage of the substances into the system of vegetable 

 being, and, of necessity, their consequent absorption by the roots ; the 

 young stems having been always cut above the surface of the sponge, and 

 apart from the roots. It is not, therefore, the mere root that is affected, 

 but the entire plant in its higher organisation. 



" Tufts of vegetation, similar to those, already described, were placed in 

 capsules with the following solutions : — Dilute nitric acid, hydriodate of 

 potassa, and chlorate of potassa. These are arranged in their relative 

 order as to their comparative permanence ; the tuft placed in dilute nitric 

 acid having fallen first, and that in chlorate of potassa remaining longest 

 unaffected. The stems of that with nitric acid slightly reddened litmus 

 paper, when macerated in distilled water ; that in hydriodate of potassa 

 gave an abundant yellow precipitate with acetate of lead ; and that from 

 chlorate of potassa deflagrated like nitre, on an ignited disc of platinum. _ 



" I would not, however, be supposed as inferring, from the last experi- 

 ment, that, though chlorate of potassa does in quantity injure vegetation 

 when thus applied to the roots, a small portion in solution might not occa- 

 sionally be beneficial, and act (in some plants, at least) as a stimulus to 

 vegetation. Last season, when all my carnations seemed rapidly proceed- 

 ing to destruction, in consequence of the arid summer (1826), and many 

 had already perished, I succeeded, by a few waterings with solution of 

 nitre (an analogous salt), not only to save the remainder, but to impart to 

 them a beautiful luxuriance of growth. The effect was very manifest, and 

 remarkably prompt ; and I now possess a hundred very beautiful plants." 



70. Account of the Mode of Culture adopted at Cunnoquhie in 

 raising Pine-apples and Melons in a Pit heated by Steam, tvith a 

 Description of the Pit and Steam Apparatus. By Mr. Alexander 

 Smith, Gardener to Colonel George Paterson of Cunnoquhie. 



The pit was erected in 1824, on a plan furnished by Mr. 

 Hay of Edinburgh, founded on a principle of heating devised 

 by Mr. Hay more than twenty years previous to that time. The 

 pit contains a bed, 2 ft. in depth, of small water-worn stones, 

 or pebbles, which are heated by pipes of steam. Over the 

 bed of pebbles is placed a cover of Arbroath pavement, sup- 

 ported on brick pillars. The boiler is of copper, with a large 

 iron pipe, which lies in the bottom along the . middle of the 

 bed of stones, and is perforated at certain distances with holes 

 for diffusing the vapour among the stones. The bottom of 

 what is destined to be the plant-bed is paved ; but " intervals 

 are left between the edge of the pavement and the wall, in 

 order to allow the steam to communicate with flues which are 



